Crushing and bending of sections of members

ABSTRACT

A method of crushing and bending an end section or an intermediate section of a tube comprises placing in a cradle of a die of a press a part of the tube including the section, and moving a punch of the press towards the die such that the section and the remainder of the tube part are bent one relatively to the other and one wall portion of the section is crushed inwardly towards a diametrically opposite wall portion of the section. The tube having a section so crushed and bent can be connected to another tube, for example, by disposing the section face-to-face with a complementarily shaped portion of the other tube such that the remainder of the part extends away from the latter portion, and then, for example, welding or bolting the section to the other tube.

Elite States atet Stanley Sept. 5, 1972 [54] CRUSHING AND BENDING OF1,823,028 9/1931 Caldwell ..113/1 16 SECTIONS OF MEMBERS PrimaryExaminer-Lowell A. Larson [72] Inventor. Kenneth Ernest Stanley 1, GreenAcre, Aylesbury Englami Attorney-Waters, Roditi, Schwartz & Nissen [22]Filed: Jan. 6, 1970 [57] ABSTRACT PP N03 935 A method of crushing andbending an end section or an intermediate section of a'tube comprisesplacing in [30] Foreign Application Priority Data a cradle of a die of apress a part of the tube including the section, and moving a punch ofthe press towards 1969 Great Bmam "998/69 the die such that the sectionand the remainder of the tube part are bent one relatively to the otherand one "72/369, 29/ wall portion of the section is crushed inwardlytowards n a diametrically opposite wall portion of the section. Field Of'r tube having a Section so crushed and bent can be 72/380 29/150113/116 116 UT connected to another tube, for example, by disposing thesection face-to-face with a complementarily [56] References and shapedportion of the other tube such that the UNITED STATES PATENTS remainderof the part extends away from the latter portion, and then, for example,welding or bolting the 2,285,275 6/ 1942 Harder ..72/369 Section to theother tube 774,159 11/1904 Cook ..29/150 3,374,532 3/1968 Zenhausern..72/369 17 Claims, 37 Drawing Figures 5A 5 2 5.1 "i," v

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sum IBM 13 PATENTEDSEP 5 m2 SHEET 13UF 13 CRUSHING AND BENDING OFSECTIONS OF MEMBERS According to one aspect of the present invention,there is provided a method of crushing and bending a section of anelongate member, comprising placing in a die of a press a part of saidmember including said section, and moving one of said die and a punch ofsaid press towards the other, such that said section and the remainderof said part are bent one relatively to the other and one wall portionof said section is crushed inwardly towards a diametrically oppositewall portion of said section.

According to another aspect of the present invention, there is provideda method of connecting together an element and a member having a crushedand bent section and produced by the method set out above, wherein saidcrushed and bent section is disposed faceto-face with a complementarilyshaped portion of said element such that said remainder extends awayfrom the latter portion, and then said member is connected to saidelement by connecting means.

Although the elongate member to which the present crushing and bendingmethod is applied is preferably a metal tube, nevertheless it could be asolid rod of suitable material, or it could be a member of plasticsmaterial deformable by impact.

In order that the invention may be clearly understood and readilycarried into effect, reference will now be made, by way of example, tothe accompanying drawings, in which:

FIG. 1 shows a side elevation of a punch and a die of a press in use ina method of crushing and bending an end section of an elongate member,in this case a metal tube, but before crushing and bending of the endsection,

FIG. 2 shows a sectional view taken on the line II--II of FIG. 1, butwith the end section crushed and bent,

FIG. 3 shows a side elevation of a joint between the tube and anelement, in this case another tube, and incorporating the crushed andbent end section,

FIG. 4 shows a sectional underneath plan view of the oint,

FIG. 5 shows a diagrammatic perspective view of a modified tube usablein thejoint,

FIG. 6 shows a view similar to FIG. 5 of another modified tube usable inthe joint,

FIG. 7 shows a perspective view of a tube according to FIG. 5 havingpunched holes,

FIG. 8 is a diagrammatic perspective view of two elements, in this caserods, interconnected by a tube to each end of which has been applied thecrushing and bending method,

FIG. 9 is plan view of a part of a geodetic structure formed of anetwork of identical tubes to each end of each of which the crushing andbending method has been applied,

FIG. 10 is a plan view of one of the tubes of this.

structure,

FIG. 1 l is a side elevation ofthe tube of FIG. 10,

FIG. 12 is a perspective view of a modified version of the joint of FIG.3, but with the two tubes shown disconnected,

FIG. 13 is a side elevation of another modified version of thejoint ofFIG. 3,

FIG. 14 is a plan view of a strap of the version of FIG. 13,

FIG. 15 is a section on the line XV-XV of FIG. 14,

FIG. 16 is a perspective view from above of a further modified versionof the joint of FIG. 3,

FIG. 17 is a sectional underneath plan view of the version of FIG. 16,

FIG. 18 is a perspective view of a joint incorporating a short tube towhich has been applied the crushing and bending method with crushing ofthe tube along its whole length,

FIGS. 19 to 23 are side elevations of respective different manners ofimproving the rigidity of joints including the crushed and bent endsection,

FIG. 24 is a side elevation of a modified version of the punch and dieof FIG. 1 in use in a modified version of the method of FIG. 1,

FIG. 25 is a sectional end view of the punch and die of FIG. 24,

FIG. 26 is a section on the line XXVI-XXVI of FIG. 24, but omitting atubeto which the method is being applied,

FIG. 27 is a fragmentary plan view of a tube to which the method of FIG.24 has been applied,

FIG. 28 is a side elevation of another modified version of the punch anddie of FIG. 1 in use in a modified version of the method of FIG. 1,

FIG. 29 is a section on the line XXIX-XXIX of FIG. 28,

FIG. 30 is a perspective view of one end of a metal tube to which endhas been applied the crushing and bending method of FIG. 28,

FIG. 31 is a side elevation of a joint between that tube and anothertube,

FIG. 32 is a perspective view of a further modified version of the punchand die of FIG. 1 for use in a modified version of the method of FIG. 1,

FIG. 33 is a side elevation of a joint incorporating a tube to which hasbeen applied the crushing and bending method ofFIG. 32,

FIG. 34 is a section on the line XXXIVXXXIV of FIG. 33,

FIG. 35 is a framework incorporating tubes to which have been appliedthe methods of FIGS. 1 and 32,

FIG. 36 is a perspective view of a joint between the tube of FIG. 33 andan element, in this case a plate, and

FIG. 37 is a section on the line XXXVII-XXXVII of FIG. 36.

Referring to FIGS. '1 and 2, the punch I has a horizontal cross-sectionas shown in FIG. 2, namely that of a rectangle 1A with a segment 18 of acircle added at one of its shorter sides. Its vertical section in aplane perpendicular to the plane of FIG. 1 is basically of the sameshape as its horizontal section. The die 2 is formed with a cavity 3 andhas fixed thereto an upright block 4 serving both as a guide for thepunch 1 and as an end stop for the tube 5. The cavity 3 is of ahorizontal section similar in size and shape to that of the punch 1,except that its horizontal section is lengthened at 3A to take a doublethickness of the tube wall of the tube 5 and is widened slightly at 3Bto provide clearances for taking account of the spread of the metal ofthe tube. That wall 3C of the cavity furthest from the block 4 isconcave and part-cylindrical. The uppermost surface of the die 2 isformed with a semi-cylindrical recess 6 forming a cradle for receivingthe end part 5A of the tube 5. The tube 5 is clamped in the recess 6 bysome clamp means (not shown) which can consist either of a clamp securedto the die 2, or of a spring-loaded pin mounted on the punch block andclamping the tube during the descent of the punch l. The recess 6 mergessmoothly into the cavity 3 at a surface of minimum radius y shown inFIG. 1. At its side furthest from the block 4, the leading end of thepunch l is formed with a rounded corner 1C at which the convexpart-cylindrical face ID of the circular segment 13 merges with theconvex part-cylindrical underneath face 1E of the punch.

In the crushing and bending method, the end part A of the tube 5 isplaced in the die 2 such that the end part 5A overlaps the cavity 3 andthe end section SE to be crushed and bent lies substantially directlybetween the cavity 3 and the punch 1. After clamping of the tube 5 inthe recess 6, the punch l is lowered vertically into the cavity 3 and inso doing bends downwardly the end section 5B, relatively to theremainder of the tube, into a position against the part-cylindrical wall3C of the cavity 3 and simultaneously crushes the end section SBradially of itself against the wall 3C. The section 5C of the tube 5adjacent to the section 5B remains unbent and uncrushed, although thereis of course a short transitional section between the sections 5B and5C.

FIGS. 3 and 4 show the crushed and bent end section 58 fitted tightlyagainst a vertical tube 7 of the same external diameter as the tube 5.The end section 58 is drilled or pierced, and the tube 7 is drilled orpierced diametrically, to receive a bolt 8 having a radiussed head.Co-operating with the bolt 8 to fix the tubes 5 and 7 together is aradiussed washer 9 and a nut 10. Radiussing of the head of the bolt 8and of the washer 9 increases the stability of the joint. Alternatively,the end section 5B is pierced with a shouldered punch so as to provide aflat on which the nut can sit. Because of the dome so formed, thestrength of the end section 58 is thereby considerably increased.

By using the described method to crush and bend an end section of athree-fourths inch outside diameter x.040 inch electrically resistancewelded steel tube, a radius y of five-sixteenths inch has been obtainedwithout rupturing of the tube.

The crushing and bending method described is a cheap and simple way ofpressing the end section of the tube to form a U-channel so that anothertube can be mated and secured to it at an angle by bolting, rivetting,welding, or brazing, for example. Because of the stresses set up in themanufacture of welded steel tubes, it is desirable to place such a tubein the die of the press tool such that the seam weld lies on a neutralaxis with .:gard to the forming forces applied to it by the punch anddie, otherwise the tube may split along the weld. When the press isoperated, the punch descends and collapses the upper portion of the wallof the end section of the tube and swages it into the U-channel formrequired. For releasing the finished component, a conventional presstool technique, such as ejector pins, is used. Only one cycle of thepress is required to produce the finished component.

The example described with reference to FIGS. 1 to 4 has the followingadvantages:

1. Products made of T-jointed tubing are cheaper to produce with thismethod than when their T-joints are formed by known methods.

2. A press with simple press tools and commonly available in industry isused to crush and bend the ends of tubes, instead of expensive bendingmachines being required to be used.

. Because the bend in the tube can be of relatively small radius, theaxis of the main section of the tube can be relatively near to the axisof a bolt used for securing it to another tube. This gives increasedrigidity of the joint produced.

. By using the described T-joint in tubular products substantial savingson packaging and freight costs can beobtained because the products canbe designed as knock-down products for assembly by the customer.

5. The T-joint described is sufficiently rigid to replace weldedT-joints in many products such as tubular furniture, car seats, roofracks, toys and benches. Moreover, the products can be made more quicklyand by unskilled labor.

If desired, opposite end sections of the tube 5 can be simultaneouslyformed as shown in one cycle of the press merely by incorporating twoidentical punches and two identical dies in one tool set. Similarly, anumber of tubes can be correspondingly formed at one or both ends byhaving single or double sets of press tools placed side-by-side. It willbe appreciated that the number of tubes which can be so formed in onecycle will depend mainly on the ease with which the tubes can be loadedinto and removed from the die set, the tonnage of the press concerned,and the diameter, wall thickness and material of the tubing.

To allow considerable variation in the position of the end section 58relatively to the tube '7, the latter can be of the form shown in FIG. 5or 6, in which the tube is drilled or pierced with a plurality of pairsof diametrically opposite through holes 30. The pairs of holes arespaced apart along the tube by the axial distance a which is, forexample, three-fourths inch in FIG. 5, and one-half inch in FIG. 6; andare regularly staggered through a constant angle a which is for example,in FIG. 5, and 60 in FIG. 6. The holes 30 are preferably made bypunching using two diametrically opposite punches to make each pair ofholes, the two punches being moved towards each other from outside thetube, but being stopped before they reach the tube axis. FIG. 7 shows atube having its holes 30 arranged according to FIG. 5 and formed by suchpunching, the resulting burrs 31 being produced on the inside of thedimpled holes 30.

Tubes as shown in FIG. 5, 6 or 7, are very suitable for use as the tubesof a system of interconnected tubes, and whereas the joints between thetubes are advantageously of the form shown in FIGS. 3 and 4, other formsof joints can be used as well.

It will be appreciated that the crushed and bent end section 58 can beof many different shapes and be made at many different angles to theremainder of the tube 5 merely by changing the shapes and orientationsof the forming faces of the punch and the die.

FIG. 8 shows the tube 5 connected between two rods 32 which areperpendicular to each other. It will be un derstood that in this casethe two crushed and bent end sections 58 of the tube 5 also extendperpendicularly to each other.

Tubes each having its opposite end sections crushed and bent andextending in respective opposite directions are particularly suitablefor use in a geodetic structure, for example a dome framework as shownin FIG. 9. In this structure the tubes are distributed in groups, thetubes of each group being equi-angularly spaced through an angle x in astar formation. Each tube extends from the center of one star formationto the center of another and has each section 58 thereof fastened, forexample bolted or welded, to the uncrushed, unbent section 5C of anadjacent tube 5. An individual tube 5 of the structure of FIG. 9 isshown in FIGS. 10 and 11. The angle x between the end section 513 andthe adjacent section 5C of the tube 5 is equal to the angle between eachtwo adjacent tubes of the structure in FIG. 9, the angle x in the caseshown being 60. FIG. 11 illustrates that the tube 5 is bent to the formof a circular arc of a radius equal to the radius of the dome. Thebending of the whole tube 5 for this purpose can be performed eitherbefore or after crushing and bending of the end sections 58. A preferredmethod of. forming a section 58 at 60 to the section 5C is firstly toapply the method of FIGS. 1 and 2 to form the crushed and bent section5B at an angle of 90 to the section 5C, and then to bend the section 5Bthrough the additional 30 in a press, for example at the same time as ahole for the bolt 8 is formed.

Referring to FIG. 12, the section 5B, after crushing and bending, hashad half-pierced therefrom four vertical lugs 40, the holes 41 beingleft by the half-piercing. Each lug 40 consists of a portion 40A of aheight equal to the height of vertical rectangular slots 42 through thewall of the tube 7, and a portion 40B of less height than the slots 42and disposed between two notches 40C formed in the top and bottom edgesof each lug 40. Each portion 40A is attached to the section 58 by way ofthe adjacent portion 408. Each hole 41 has a pair of lugs 40half-pierced therefrom, and the lugs of each pair extend parallel toeach other, the spacing between their outside faces being virtually thesame as the horizontal width of each slot 42. The slots 42 are regularlystaggered through a constant angle about the axis of the tube 7 and arespaced a constant distance apart along the tube. The spacing between anytwo slots 42 disposed one vertically above the other is equal to thespacing between the pairs of lugs 40. Thus, the pairs of lugs 40 canhave their portions 40A inserted through two slots 42 of which one isdisposed vertically above the other, and then the tube 5 is lowered suchthat the bottom edges of the two slots 42 in question engage with thenotches 40C in the bottom edges of the lugs 40. The tube 5 is nowprevented by the lugs 40 from moving relatively to the tube 7 in anymanner except upwardly.

In FIGS. 13 to 15, the connection between the tube 5 and the tube 7 isinfinitely adjustable along the tube 7. For this purpose, the tube 5 isconnected to the tube 7 by solely an endless steel strap 43 embracingthe tubes 5 and 7. A portion 43A of the strap 43 bears against theinside of the bend at the adjacent end of the tube 5, while the oppositeportion 433 of the strap 43 engages the tube 7. The portion 43B is ofelongate cross-section with a sharp inside edge 43C engaging the tube 7,and the portion 43A may be of identical cross-section if so desired, butthose portions of the strap 43 joining the portions 43A and 43B are ofcircular cross-section. It will be understood that application to thetube 5 of a downward load as indicated by the arrow L in FIG. 13 willcause the edge 43C to bite into the outside surface of the tube 7 andthus prevent the tube 5 from sliding down the tube 7 under the load,but, nevertheless, on removal of the load, the tube 5 and the strap 43can be readily adjusted to any desired position along the tube 7Referring to FIGS. 16 and 17, the section 58 is modified in having itslongitudinal edges 44 turnedback. This is achieved by suitable shapingof the forming faces of the punch I and the die 2, the turned-backlongitudinal edges being formedsimultaneously with the crushing andbending of the section 5B. The edges 44 are substantially parallel toeach other and to a plane containing the axes of the tubes 5 and 7,which are perpendicular to each other. However, the edges 44 are obliqueto the axis of the tube 7, which axis of course extends in the directionof movement of the punch l relatively to the die 2. The tube 7 isembraced by a short channel-form piece 45 which has its freelongitudinal edges 46 parallel to each other and to the edges 44 andturned inwardly. The edges 44 and 46 extend downwardly and outwardlyaway from the base of the piece 45. An internally threaded nipple 47 inthe base of the piece 45 receives a grub screw 48 for tightening againstthe outside surface of the tube 7. The upper rim 49 of the piece 45 isthickened to be capable of receiving hammer blows without deformation.To secure the tube 5 to the tube 7, the section 58 is placedface-to-face against the tube 7 as shown, and then the piece 45 islowered to engage its edges 46 behind the edges 44. Thereupon, the piece45 is driven downwardly by hammer blows to press the section 58 firmlyagainst the tube 7 by the wedging action of the edges 44 and 46.Finally, the grub screw 48 is tightened to prevent the piece 45 frombeing accidentally knocked upwardly. It will be appreciated that thetube 5 can be adjusted to any desired position along the tube 7 afterrelease of the screw 48 and the wedging action.

The joint shown in FIG. 18 consists of two metal rods 50 and 51 whichare of circular cross-section and are disposed perpendicularly to eachother. These are connected together by a crushed and bent short metaltube 52 welded to the rods 50 and 51. The member 52 has been formed in apunch-and-die arrangement such as is shown in FIGS. 1 and 2, except thatthe punch I has an extension of which the lowermost face issemi-cylindrical and enters the recess 6 to crush the remainder of theshort tube at the same time as the end section of the short tubecorresponding to the end section 58 is crushed and bent. The formingfaces of the punch are of a radius identical to the radius of the rods50 and 51, whereby the member 52 fits snugly on the rods 50 and 51.

It may be that in certain circumstances a joint such as shown in FIGS. 3and 4 is not sufficiently rigid. In that case, as shown in FIG. 19, thejoint can be strengthened by providing through the tube 7 a self-tappingscrew 53 screwed into metal of the outside of the bend in the tube 5. Aspacer 54 limits pulling of the tube 5 towards the tube 7 by the screw53. The screw 53 is of course disposed as far as practicable from theaxis 8' of the bolt 8.

In FIG. 20, the section 58 is shown projectionwelded at 55 to the tube7. To strengthen the joint, a member 52 as shown in FIG. 18 isillustrated projection-welded to the tube 7 and to the uncrushed, unbentsection C of the tube 5.

Another manner of strengthening the joint of FIGS. 3 and 4 is shown inFIG. 21, in which a gaiter S6 encircles the section 5C of the tube 5 andis fixed thereto in some manner, for example shrink-fitted thereto. Thegaiter 56 has an extension 56A which fits snugly against the outsidesurface of the tube 7 and tends to prevent turning of the tube 5 aboutthe axis 8' in both senses.

FIG. 22 shows a version in which a short length of tube 57 has beeninserted in the end of the tube 5 before crushing and bending of thesection 58 and has thus been crushed and bent simultaneously with thatsection.

With regard to FIG. 23, the joint between the tubes 5 and 7 is againstrengthened using the member 52, but this time the parts 5, 7 and 52are fixed to one another solely through rings 58 crimped or otherwisesecured thereto.

Under certain conditions, it may be required that one of thelongitudinal edges of the section 58 should project further than theother from the uncrushed, unbent section SC in an axial direction of thesection 5C, while, nevertheless, these longitudinal edges remainparallel to each other and the section 58 remains of circular arc shapein cross-section. Such a version is shown in FIG. 27 and is producedusing the punch 1 and the die 2 of FIGS. 24 to 26. In this, the verticalpart-cylindrical forming face ID of the punch, and the correspondingvertical part-cylindrical forming wall 3C of the recess 3 are offsetrelatively to the vertical plane containing the axis of the recess 6.The lowermost face 15 of the punch l is again radiussed to promote theprogressive collapse of the section SB of the tube 5 during crushing andbending. There is of course provided between the face 1D and the wall 3Cas seen in plan a gap 59 to receive two thicknesses of the wall of thetube 5.

With the tube 5 already described, the tube 7 is received at the outsideof the bend in the tube 5. It may be desired instead to have the tube 7received at the inside of the bend in the tube 5, as shown in FIG. 31,in which the crushed and bent end section SF of the tube 5, while stillof U-channel shape and fitting snugly against the outside surface of thetube 7, has its concave external surface facing towards the tube 5. Thisformation at the end of the tube 5 can be obtained by means of the punchl and the die 2 shown in FIGS. 28 and 29. The punch 1 has a verticalpart-cylindrical concave face 1F merging at its lower end with ahorizontal part-cylindrical concave face 10. The forming vertical wall3D of the recess 3 is of part-cylindrical convex shape and is thuscomplementary to the face 1F The wall 3D merges into the wall of thepart-cylindrical recess 6 of the die 2. When the punch 1 is lowered intothe recess 3, the face promotes the downward bending of the end section5F relatively to the remainder of the tube 5, and later the face 1Fcontinues the downward bending of the end section 5F and. crushes itagainst the wall 3D, so that the end of the tube to which this methodhas been applied takes on the appearance shown in FIGS. 28 to 30. Thereis of course provided between the face IF and the wall 3D as viewed inplan a gap 60 dimensioned to receive two thicknesses of the wall of thetube 5.

It will be understood that the end section 5F may be fixed to the tube 7by bolting as indicated at 8' in FIG. 31, rivetting, welding, orbrazing, for example.

It may be desired to provide a joint in which, instead of an end sectionof a tube being mated to a complementarily shaped portion of an elementas already described, an intermediate section of the tube is mated tothis complementarily shaped portion. This can be achieved using thepunch and die which are shown in FIG. 32 and which produce, on a tube 5as shown in FIGS. 33 and 34, a crushed intermediate section 61 which isbent relatively to the remainder of the tube 5. This section 61 has itscross-section of the shape of a circular arc and has its concaveexternal surface at the outside of the bend in the tube 5, whereby thetube 7 is received at the outside of this bend. FIG. 32 shows the punchand die for use in producing the crushed section 61 of the tube 5.Formed in the top surface of the die are two co-axial part-cylindricalrecesses 71 having their axis horizontal and forming respective cradlesfor receiving the tube 5. Also formed in the die 70 is a recess 72 whichis much deeper than the recesses 71 and which has at its bottom aforming wall 73 of convex part-cylindrical shape, the axis of the wall73 being horizontal and lying in the same vertical plane as thatcontaining the axis of the recesses 71. Joining the ends of the wall 73to the inner ends of the walls of -the recesses 71 and merging smoothlytherewith are two semi-cylindrical concave walls 74, the axes of whichconverge downwardly. The punch 75 is guided so as to be verticallydisplaceable and is formed at its underneath with a concave,part-cylindrical forming face 76 which, in the fully lowered position ofthe punch 75, covers the forming wall 73 at a spacing therefrom equal totwo thicknesses of the wall of the tube 5. Merging at their lower endswith the face 76 are two semi-cylindrical faces 77 which are provided atrespective opposite sides of the punch 75 and which have their axesparallel to the axes of the walls 74. When the punch 75 is in its fullylowered position, the axes of the faces 77 in fact coincide with therespective axes of the walls 74. In use of the punch and die of FIG. 32,a straight part of the tube 5 is laid in the recesses 71 with anintermediate section of this straight part extending over the recess 72.The punch is now lowered so that the face 76 contacts the intermediatesection and displaces it downwardly. This causes the two sections of thetube 5 disposed axially outwardly of the face 76 to bend in a verticalplane upwardly towards the faces 77 until they are encircled by thewalls 74 and the faces 77 in the lowermost position of the punch 75.Simultaneously, the intermediate section is crushed between the wall 73and the face 76 to assume the shape shown in FIGS. 33 and 34.

By simply altering the radius of the wall 73, the radius of the concaveexternal surface of the crushed section 61 can be adapted to the radiusof the tube 7 on which it is to be seated.

A tube 5 formed with a crushed intermediate section 61 and two crushedend sections 58 is particularly useful in the construction oflattices,such as shown in FIG. 35, in which two tubes 5 are fixed by way of thescctions 58 and 61 between two parallel supporting tubes 7.

Both the end section 58 and the intermediate section 61 may mate with acomplementarily shaped portion which has been displaced out of the planeof a plate. FIGS. 36 and 37 shows such an arrangement in respect of theintermediate section 61. Here, a so-called hogback 84) has been pressedout of a plate 81, and holes have been punched out of the hogback 80 andthe section 61 and have been aligned to receive the bolt 82 of anut-and-bolt connection 82, 83. The hole in the section 61 for receivingthe bolt 82 may be formed either after the crushing of the section 61,or be formed simultaneously with that crushing.

The joints described with reference to the drawings have the advantagethat their shapes facilitate brazing and soldering because of thecapillary attraction set up between the tubes and 7 to be joined.Another advantage is that, simultaneously with crushing of the section5B or 61, projections can be readily formed on the section to enable itto be speedily resistance welded to the tube 7. The major advantage ofthe examples described with reference to the drawings is that it ispossible to mass produce crushed and bent tubes and rods with their costof production and the radii of curvature of their bends being much lessthan with known methods.

In order to reduce the friction between the corner 1C and the tube 5during crushing and bending in the version of FIGS. 1 and 2, and thus toreduce roughening of the surface of the tube 5, it is possible to mountin the corner 1C a wheel or ball which corresponds in radial section tothe corner 1C and rolls on the tube 5 during crushing and bending. Asimilar modification may of course be made in the versions of FIGS. 24to 26, FIGS. 28 and 29, and FIG. 32.

It may in certain circumstances be desired to have a fluid flow throughthe joint shown in FIG. 10, for example. In practice, it has been foundthat the free end of the section 5B can be made fluid-tight by thecrushing described, while the opposite end of the section 58 remains notfluid-tight. Thus, by forming two holes, one in the inner wall of thesection 58 at this opposite end, and the other in the wall of the tube7, the interior of the section 5C has been communicated with theinterior of the tube 7. The holes were formed prior to assembly andwelding of the joint, during which a compressible sealing ringencircling the two holes was inserted and compressed between the innerwall of the section 58 and the wall of the tube 7. Fluid was then ableto flow through the tubes 5 and 7, the sealing ring preventing leakageof the fluid from the gap between the two walls.

WHAT I CLAIM IS:

I. A method of crushing and bending a section of a tube comprisingplacing in a die of a press a part of said tube including said section,and moving one of said die and a punch of said press towards the otherto crush one wall portion of said section inwardly towards adiametrically opposite wall portion of said section so that said sectionacquires a double-walled channel form extending along said section andto bend said section and the remainder of said part one relative to theother so that said remainder extends from the base of said channel in adirection away from the mouth of said channel.

Ill)

2. A method according to claim 1, wherein after the crushing, each ofsaid one wall portion and said opposite wall portion is of across-sectional shape of substantially the form of a circular arc.

3. A method according to claim ll, wherein after the crushing, each ofsaid one wall portion and said opposite wall portion is of substantiallyconstant crosssection throughout its length.

4. A method according to claim 1, wherein said part and said section arean end part and an end section, respectively, and said end part isplaced in said die such that said end part overlaps a recess in said dieand that said end section lies substantially directly between saidrecess and said punch, and one of said die and said punch is movedtowards the other such that said punch penetrates said recess and in sodoing bends said end section, relatively to said remainder, into aposition against a suitably shaped wall of said recess andsimultaneously crushes said end section radially against said wall.

5. A method according to claim 4, wherein said wall of said recess isconcave, and said punch has a convex face which crushes said sectionagainst said wall.

6. A method according to claim 5, wherein said face and said wall areeach asymmetrical throughout their lengths with respect to a planeextending in said direction and containing the longitudinal axis of saidpart when placed in said die, whereby said section after drushing andbending has its longitudinal central plane oblique to that of saidremainder.

? 7. A method according to claim 4, wherein said part is placed in saiddie such that it is supported by a cradle df said die, said cradleextending transverse to the direction of movement of said one of saidpunch and said die towards the other, and said wall extending in a planewhich extends in said direction and passes through said cradle, and awayfrom a position occupied by said punch immediately prior to the crushingand bending.

8. A method according to claim 7, wherein said wall extends in saiddirection.

9. A method according to claim 7, wherein said punch and said die are soshaped that, simultaneously with the crushing and bending of saidsection, said section is formed with turned-back 10. A method accordingto claim 1, wherein said section is an intermediate section of saidtube, and said part is placed in said die such that said part extendsacross a recess in said die and that said section lies substantiallydirectly between said recess and said punch, and one of said die andsaid punch is moved one towards the other such that said punchpenetrates said recess and in so doing displaces said section into aposition against a suitably shaped wall of said recess andsimultaneously therewith bends said remainder relatively to said sectionand crushes said section radially against said wall.

11. A method according to claim 10, wherein said wall of said recess isconvex, and said punch has a concave face which crushes said sectionagainst said wall.

12. A method according to claim 10, wherein said part is placed in saiddie such that it has two end sections supported by respective cradles,said wall and said cradle extending in approximately the same directionas one another and transversely to the direction of movement of said oneof said punch and said die towards the other.

said remainder.

16. A method according to claim 1, and preceded by inserting within saidsection a section of a second tube, the crushing and bending of thefirst-mentioned section being accompanied by corresponding crushing andbending of said section of said second tube.

17. A method according to claim 1, wherein said punchcomprises a rollingmember arranged to roll on said section during the crushing and bending.

1. A method of crushing and bending a section of a tube comprisingplacing in a die of a press a part of said tube including said section,and moving one of said die and a punch of said press towards the otherto crush one wall portion of said section inwardly towards adiametrically opposite wall portion of said section so that said sectionacquires a double-walled channel form extending along said section andto bend said section and the remainder of said part one relative to theother so that said remainder extends from the base of said channel in adirection away from the mouth of said channel.
 2. A method according toclaim 1, wherein after the crushing, each of said one wall portion andsaid opposite wall portion is of a cross-sectional shape ofsubstantially the form of a circular arc.
 3. A method according to claim1, wherein after the crushing, each of said one wall portion and saidopposite wall portion is of substantially constant cross-sectionthroughout its length.
 4. A method according to claim 1, wherein saidpart and said section are an end part and an end section, respectively,and said end part is placed in said die such that said end part overlapsa recess in said die and that said end section lies substantiallydirectly between said recess and said punch, and one of said die andsaid punch is moved towards the other such that said punch penetratessaid recess and in so doing bends said end section, relatively to saidremainder, into a position against a suitably shaped wall of said recessand simultaneously crushes said end section radially against said wall.5. A method according to claim 4, wherein said wall of said recess isconcave, and said punch has a convex face which crushes said sectionagainst said wall.
 6. A method according to claim 5, wherein said faceand said wall are each asymmetrical throughout their lengths withrespect to a plane extending in said direction and containing thelongitudinal axis of said part when placed in said die, whereby saidsection after crushing and bending has its longitudinal central planeoblique to that of said remainder.
 7. A method according to claim 4,wherein said part is placed in said die such that it is supported by acradle of said die, said cradle extending transverse to the direction ofmovement of said one of said punch and said die towards the other, andsaid wall extending in a plane which extends in said direction andpasses through said cradle, and away from a position occupied by saidpunch immediately prior to the crushing and bending.
 8. A methodaccording to claim 7, wherein said wall extends in said direction.
 9. Amethod according to claim 7, wherein said punch and said die are soshaped that, simultaneously with the crushing and bending of saidsection, said section is formed with turned-back
 10. A method accordingto claim 1, wherein said section is an intermediate section of saidtube, and said part is placed in said die such that said part extendsacross a recess in said die and that said section lies substantiallydirectly between said recess and said punch, and one of said die andsaid punch is moved one towards the other such that said punchpenetrates said recess and in so doing displaces said section into aposition against a suitably shaped wall of said recess andsimultaneously therewith bends said remainder relatively to said sectionand crushes said section radially against said wall.
 11. A methodaccording to claim 10, wherein said wall of said recess is convex, andsaid punch has a concave face which crushes said section against saidwall.
 12. A method according to claim 10, wherein said part is placed insaid die such that it has two end sections supported by respectivecradles, said wall and said cradle extending in approximately the samedirection as one another and transversely to the direction of movementof said one of said punch and said die towards the other.
 13. A methodaccording to claim 12, wherein said two end sections swing out of thecradles towards said punch during the crushing and bending.
 14. A methodaccording to claim 12, wherein said wall and said cradles extendperpendicularly to said direction of movement.
 15. A method according toclaim 1, wherein the crushing and bending of said section is accompaniedby the crushing of one wall portion of said remainder inwardly towards adiametrically opposite wall portion of said remainder.
 16. A methodaccording to claim 1, and preceded by inserting within said section asection of a second tube, the crushing and bending of thefirst-mentioned section being accompanied by corresponding crushing andbending of said section of said second tube.
 17. A method according toclaim 1, wherein said punch comprises a rolling member arranged to rollon said section during the crushing and bending.